There is conventionally known a printer that prints one or more characters on a printing medium. Specifically, Japanese Patent Application Publication No. H9-216393 discloses a printer that prints an image on a film as a printing medium. This printer includes a thermal head, a platen roller, and a guide. The thermal head is arranged to face the platen roller. The guide is positioned upstream of the thermal head and the platen roller in a conveying direction of the film. The guide linearly extends toward a contact position between the thermal head and the platen roller. The film guided by the guide is nipped between the thermal head and the platen roller, and an image is printed on the film while the film is conveyed in the conveying direction.